The effect of temperature and pressure on the spin state of cobalt ions in La(1-x)Pr(x)CoO(3)compounds


The crystal structure, magnetic susceptibility as a function of temperature chi(T) in the range 5-400 K, and the hydrostatic pressure effect on chi at fixed temperaturesT = 78, 150, and 300 K, were studied in perovskite-like compounds La1-xPrxCoO3(x = 0, 0.1, 0.2, and 0.3). The obtained experimental data were analyzed using a two-level model with an energy gap Delta between the ground and excited states of the system that correspond to the spin valuesS = 0 and 1 for Co(3+)ions. In this model, the magnetism of Co(3+)ions, which determines the features of the chi (T) dependence, is ensured by the temperature-induced change in the population of the excited state. The anomalously large magnitude of the observed pressure effect is associated with the high sensitivity of Delta to changes in the lattice volume, under the influence of both hydrostatic and chemical pressures, when La is replaced by the smaller Pr ion in the considered system. Theoretical calculations of the electronic structure for the boundary compounds LaCoO(3)and PrCoO(3)confirm the significant increase in the excitation energy Delta with a decrease in the lattice volume, and also support the scenario of a spin crossover between the states of cobalt ions with low and intermediate spin values.






Panfilov, AS; Lyogenkaya, AA; Grechnev, GE; Pashchenko, VA; Vasylechko, LO; Hreb, VM; Kovalevsky, AV



This work was financially supported by projects CICECO-Aveiro Institute of Materials (reg. number UID/CTM/50011/2013) and POCI-01-0145-FEDER-031875, part of the state program COMPETE 2020 (Portugal), and with support of the Portuguese National Funds (FCT/MEC), POCI Operational Program (FEDER/FNR), and the Science and Technology Foundation under the State Budget (OE) of Portugal. Part of the work was also funded by the Ministry of Education and Science of Ukraine as part of project no. 0118U000264 Ferit, and the Ukraine budget program No. 6541230. This work was performed using the computing resources of the B.I. Verkin ILTPE grid cluster, part of the NAS of Ukraine, Kharkov.

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